These stamps are forgeries of overprints issued in the latter part of 1880 for the monastic Republic of MOUNT ATHOS in the south of Macedonia. Many monks settled in this area and the earliest monastary was founded in 963 and the latest in 1542.
The total population of monks in various places in this area was about six or seven thousand at the time that the stamps were issued. The original overprints on the Turkish stamps were apparently done by a postal official,but the postal authorities did not sanction his actions and ordered the stamps withdrawn. The length of time they were in circulation is not known exactly,but it was in thr latter half of 1880 .
Some records say these are not forgeries but later overprint issues ,but the best record is the Mekeel's vol 15 of May 5,1905 which states "The stamps surcharged for Mount Athos and the "Katschak" stamps are of very,very doubtful philatelic value,and may be ignored by collectors ".
These stamps of Turkey are overprinted with a triangle with three letters in the corner . Most mail coming out of Mt. ATHOS came thru the Russian Post Office at that location between 1880 -1913 ,then WWI started and it became Greece .